The new Music, Podcasts, and TV apps will be made using Marzipan, Apple’s new technology designed to facilitate the porting of iPad apps to the Mac without too many code changes. It’s not clear whether the redesigned Apple Books app will also be made using the technology, but given that the redesign came to iOS first and its usage for the other apps, it’s likely that this new Books app will also be using UIKit.

Nothing surprising here, but it leaves the $64,000 question unanswered: will these apps be more like dumbed-down iPad apps on the Mac, or more like smartened-up Mac apps on the iPad? Dumbed-down iPad apps on the Mac is, if anything, a generous description of the News, Stocks, Home, and Voice Recorder apps we got with 10.14.

With the standalone versions of Apple’s media apps coming to the
Mac, it’s natural to ask: what about iTunes in macOS 10.15?
According to sources, the next major version of macOS will still
include the iTunes app. Since Apple doesn’t have a new solution
for manually syncing devices such as old iPods and iPhones with
the Mac, it’s natural to keep iTunes around a little longer.

Makes sense. Let the new apps serve as front-ends to Apple’s media services, and let iTunes stay as a media player for audio and video files on your Mac.